/// Return the XY value to use for SetWhiteXY for a given camera color
/// space coordinate as the white point.
/// \param neutral A camera color space value to use for white point.
/// Components range from 0.0 to 1.0 and should be normalized such that
/// the largest value is 1.0 .
/// \retval White point in XY space that makes neutral map to this
/// XY value as closely as possible.
public DNGxyCoord NeutralToXY(DNGVector neutral)
{
const uint kMaxPasses = 30;
if (fChannels == 1)
{
return(DNGxyCoord.PCStoXY);
}
DNGxyCoord last = DNGxyCoord.D50;
for (uint pass = 0; pass < kMaxPasses; pass++)
{
DNGMatrix nullMat = null;
DNGMatrix xyzToCamera = FindXYZtoCamera(last, ref nullMat, ref nullMat, ref nullMat);
DNGMatrix inv = xyzToCamera.Invert();
DNGVector vec = inv * neutral;
DNGVector3 vec3 = new DNGVector3(vec);
DNGxyCoord next = DNGxyCoord.XYZtoXY(new DNGVector3(xyzToCamera.Invert() * neutral));
if (Math.Abs(next.X - last.X) +
Math.Abs(next.Y - last.Y) < 0.0000001)
{
return(next);
}
// If we reach the limit without converging, we are most likely
// in a two value oscillation. So take the average of the last
// two estimates and give up.
if (pass == kMaxPasses - 1)
{
next.X = (last.X + next.X) * 0.5;
next.Y = (last.Y + next.Y) * 0.5;
}
last = next;
}
return(last);
}
public DNGColorSpace(DNGMatrix3x3 toPCS)
{
// The matrix values are often rounded, so adjust to
// get them to convert device white exactly to the PCS.
DNGVector W1 = toPCS * new DNGVector3(1.0, 1.0, 1.0);
DNGVector W2 = DNGxyCoord.PCStoXYZ;
double s0 = W2[0] / W1[0];
double s1 = W2[1] / W1[1];
double s2 = W2[2] / W1[2];
DNGMatrix3x3 S = new DNGMatrix3x3(s0, 0, 0,
0, s1, 0,
0, 0, s2);
mToPCS = S * toPCS;
// Find reverse matrix.
mFromPCS = mToPCS.Invert();
}